The present invention generally relates to semiconductor processing, and in particular to a system and method for monitoring and controlling of a chemical trim process to improve critical dimension (CD) control based on fluorescence spectroscopy analysis.
In the semiconductor industry, there is a continuing trend toward higher device densities. To achieve these high densities there has been and continues to be efforts toward scaling down the device dimensions on semiconductor wafers. In order to accomplish such high device packing density, smaller and smaller features sizes are required. This includes the width and spacing of interconnecting lines and the surface geometry such as comers and edges of various features. Since numerous interconnecting lines are typically present on a semiconductor wafer, the trend toward higher device densities is a notable concern.
The requirement of small features (and close spacing between adjacent features) requires high resolution photolithographic processes. In general, lithography refers to processes for pattern transfer between various media. It is a technique used for integrated circuit fabrication in which a silicon slice, the wafer, is coated uniformly with a radiation-sensitive film, the resist, and an exposing source (such as optical light, X-rays, or an electron beam) illuminates selected areas of the surface through an intervening master template, the photomask, for a particular pattern. The lithographic coating is generally a radiation-sensitized coating suitable for receiving a projected image of the subject pattern. Once the image is projected, it is indelibly formed in the coating. The projected image may be either a negative or a positive of the subject pattern. Exposure of the coating through the photomask causes a chemical transformation in the exposed areas of the coating thereby making the image area either more or less soluble (depending on the coating) in a particular solvent developer. The more soluble areas are removed in the developing process to leave the pattern image in the coating as less soluble polymer.
Projection lithography is a powerful and essential tool for microelectronics processing. However, lithography is not without limitations. Patterning features having dimensions of about 0.25 xcexcm or less with acceptable resolution is difficult at best, and impossible in some circumstances. Patterning small features with a high degree of critical dimension control is also very difficult. Procedures that increase resolution, improved critical dimension control, and provide small features are therefore desired.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
A system and method is provided for determining and controlling development of a semiconductor substrate employing fluorescence spectroscopy. One aspect of the invention relates to a system and method employing fluorescence spectroscopy to facilitate control of a chemical trim etch process during development of a photoresist material layer. The chemical trim etch process comprises applying a trim compound or material to a patterned photoresist. The trim compound can be a gas or a solution. The trim compound or material is diffusable into the sides and top of the patterned resist. The diffused regions of the resist are soluble in a developer, which facilitates creating smaller features in the patterned photoresist. The fluorescence spectroscopy system can be employed to measure isolated and dense gratings or CDs and use the evolution of the CD to determine when to terminate the chemical trim process.
In one aspect of the invention, a signature library is provided containing a plurality of signatures corresponding to various CD measurements. A measurement signal provided by a fluorescence spectroscopy system can be converted into an actual CD measurement corresponding to a CD of one or more resist structures or features on a patterned photoresist material layer. A signature is then generated corresponding to the actual CD measurement and matched with a signature in the signature library. A trimming compound application process is then repeated and signatures matched until the appropriate match is made corresponding to the desired CD.
To the accomplishment of the foregoing and related ends, certain illustrative aspects of the invention are described herein in connection with the following description and the annexed drawings. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed and the present invention is intended to include all such aspects and their equivalents. Other advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.